Dumb story idea: dissidents in the near future using rebuilt and replica 1980s computer tech because it's so obscure and antiquated as to be virtually unhackable.
"Yes, you could easily and instantly decrypt my sensitive files, but can you read them off this floppy disk?"
The major hole in this is that parts of the federal government can upgrade verrrry slowly, so there's probably some basement dwelling FBI agent who's just like, "Sure, I'll use the 386 workstation at my desk."
"Wait, what the fuck is an amiga?"